A model poses with a 59.60-carat mixed cut diamond known as "The Pink Star", the largest Internally Flawless Fancy Vivid Pink diamond ever graded by the Geological Institute of America (GIA), ahead of being auctioned in Hong Kong next month by Sotheby's which said it could fetch upwards of $60 million (GBP £48.4 million) to make it the most expensive diamond of its kind ever sold, in London, Britain, March 20, 2017. REUTERS/Toby Melville

A model poses with a 59.60-carat mixed cut diamond known as "The Pink Star", the largest Internally Flawless Fancy Vivid Pink diamond ever graded by the Geological Institute of America (GIA), ahead of being auctioned in Hong Kong next month by Sotheby's which said it could fetch upwards of $60 million (GBP £48.4 million) to make it the most expensive diamond of its kind ever sold, in London, Britain, March 20, 2017. REUTERS/Toby Melville